The present invention relates to automatic washers, either of the front-loading or top-loading types, and more particularly to an improved washing system and control therefor.
Automatic clothes washers generally include fluid handling systems for filling a washer tub with a wash fluid consisting of a water and detergent solution, tumbling or agitating a wash load of fabrics for a period of time, then draining the wash fluid from the tub. A portion of the washing part of the cycle may include a spray treatment or pretreatment of the fabrics while the basket is spinning. A subsequent rinse with fresh water and draining of the rinse water are also provided. All or part of the rinse cycle may include a spray rinse of the fabrics while the basket is spinning at high speed.
Spray treatment of fabrics during the wash cycle therefore is known. Spray treatment may be desirable in a clothes washer because of known benefits such as improved washing performance and reduced energy and water usage. An example of a clothes washer having spray treatment is disclosed in U.S. Pat. No. 5,271,251 for example, assigned to the assignee of the present invention. In this example, however, a probe sensor provides a signal for the purpose of maintaining a predetermined water level during recirculation. Alternatively, a pressure dome or temperature thermistor may be used to detect the water level and a determination may be made for the level of water to be used in the following swirl portion of the cycle. However, there is no determination made of the amount of fabric load contained within the washer using the on or off times of the inlet valve or valves or the information provided by the pressure sensor.
There are known disadvantages to spray treatment as well. One undesirable condition which has been found to occur during a spray pretreatment portion of the wash cycle is `suds lock`. When this condition occurs, contact of the fluid with the spinning basket acts to further increase the amount of suds which thus raises the height of the sudsy fluid toward the basket. The eventual result of this unstable process is that suds build up beyond the bottom of the basket and climb between the sides of the basket and tub. This large amount of suds acting between the spinning basket and the fixed tub produces a significant drag force on the basket. This drag force is large enough to cause the clutch to slip and thus causing the basket to slow down considerably. This slipping of the clutch due to excessive suds between the spinning basket and the tub is called `suds lock`.
Certain combinations of environmental factors have been found to increase the likelihood of suds lock. Such combinations of very small loads or no load, very large doses of detergent, liquid detergent, type of detergent and soft water have been found to increase the formation of suds during the spray pretreat cycle. Also, if the means by which the amount of water controlled during the spray pretreatment cycle is not robust, suds lock may be more likely. To guard against both worst case conditions or machine degradation over time, a control for sensing suds lock and controlling the machine based on suds lock information is desirable.
U.S. Pat. No. 4,784,666, assigned to the assignee of the present application, discloses a high performance washing process for vertical axis automatic washers which includes the recirculation of wash fluid prior to the agitate portion of the wash cycle. That patent describes, as a particular embodiment of the invention, to load a charge of detergent into the washer along with a predetermined amount of water, preferably prior to admitting a clothes load into the basket to assure that the concentrated detergent solution will initially be held in a sump area of the wash tub so that the detergent will be completely dissolved or mixed into a uniform solution before being applied to the clothes load. It is also suggested that the addition of an anti foaming agent may be desirable. No particular arrangement is provided for mixing the detergent and water to provide a uniform solution, nor is any particular means described for assuring that the amount of wash liquid within the tub during the spin wash portion of the wash cycle is an appropriate amount which is slightly in excess of the saturation level for the clothes load.
U.S. Pat. Nos. 5,219,370 and 5,233,718, assigned to the assignee of the present invention, disclose variations on a high performance washing process for vertical or horizontal axis automatic washers which include the recirculation of wash fluid prior to the agitate portion of the wash cycle or other washing or rinsing steps. The primary means for controlling water input into the systems is to detect water level using a liquid level sensor. It is suggested that a pressure dome sensor may be used to detect an oversudsing condition, however this would be performed in conjunction with usage of the liquid level sensor, which is not provided for in the present invention. These patents allow for the possibility of indirectly inferring the water level in the tumble portion of the cycle based on the sensed level of detergent liquor in the pretreatment portion, unlike the present invention which determines the amount of clothes load and possibility of suds lock.